I purchased these to go with Mega Loop Mayhem. There was no information that I could find conneced with the Mega Loop Mayhem site to tell me what kind of extra cars to buy. There were ratings that all cars would not work and that only one car came with the set. So I had to buy blindly. Then I found out through another website that there was a pack of cars FOR THE MEGA LOOP MAYHEM product. It mad online buying through the Mattel Shop an expensive experience. You would expect the company site to give you the information necessary.